Piston to valve clearance - How much do I need?
 

I'm gonna have to check my clearance with my .030 shaved stock heads and this F303 cam. I'm hoping it'll be all right with 1.6 roller rockers. Anyway, how much clearance do I need to be in the safe zone in case a valve floats. I got Crane springs too that are setup for this cam.

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ICQ# 42269241
Indiana Stangers Association
Buy your parts here

No less than 0.125" for both intake and exhaust. I've seen 'em run a little tighter, but you're playing with fire if you miss a shift or over-rev the engine. Pay attention to the valve in relation to the eyebrow radius too. Alot of times the valves won't kiss at the bottom of the relief but they'll hit at the edge of the eyebrow. Be sure to check your PV clearance with a solid lifter too; it won't do any good to check it with a hydraulic lifter.

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Jeff Chambers
Trophy Stock #3
11.86 Seconds / 113.8 MPH
Chambers Racing Team

Now where am I going to get a solid lifter???

How long is a solid lifter? I'll just make one at work tonight.

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ICQ# 42269241
Indiana Stangers Association
Buy your parts here

What I've done to check P/V is remove the valve spring and replace it with light spring from a hardware store. You keep the hydraulic lifter in its place. You'll need a spring removal tool, but Crane has one that's cheap.

FWIW, I've run .100 on the intake and .800 on the exhaust without any problems. Not what I'd recommend to everyone, but it worked on my '65 289.

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Russ L
'91 LX
Procharger, 3 row intercooler, extrude honed Cobra intake, Mac full Length Headers, 30# inj., 73mm C&L, 75mm tb, E303 cam, 289 rods, ported E7 heads, MSD, T-Rex w/255 lph Walbro, 5 lug conversion, Cobra R wheels, 3.27 gears and Moser Axles.

You mean I need a valve spring compressor? No biggie if that's what you meant. I'll try the weak spring idea. Thanks man.

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ICQ# 42269241
Indiana Stangers Association
Buy your parts here

I agree with Jeff in take your measure ments on the outside of the eyebrow. Now I do have 2.02 valves but I had .139" clearance and after I got the motor apart I saw a slight mark where the valves had kissed the piston on the very, very edge of the eyebrow. Now since I fly cut them it is not a issue. I was always told .100 on the intake and exahaust as a min.

You can take some epoxy and fill a roller lifter or weld one shut to make a solid lifter.

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You can make a solid roller lifter by taking a hydraulic roller lifter apart and flipping the plunger over. Its kind of tough to get the retaining clip back in, but its a solid lifter when you're done. Just remember that when you're checking it with solid lifters, only tighten the rocker arm finger tight (with the roller on the base circle)...don't preload it like you do when you're assembling your valve train.

I was on the phone with Comp Cams today, and their recording says minimum PV is 0.100" for both. I've always been told 0.125" so I guess my motor man is a little more conservative. Buy hey, I haven't kissed a valve so I guess he's alright in my eyes!

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Jeff Chambers
Trophy Stock #3
11.86 Seconds / 113.8 MPH
Chambers Racing Team